DESCRIPTION: (Applicant's Description) Prostate Cancer is the most common cancer in U.S. men. The disease has a unique association with ethnic background - the highest incidence and mortality risk in African Americans, an intermediate risk in European-Americans, and a significantly lower risk among Hispanics, notably Mexican Americans who constitute the largest proportion of Hispanics in the U.S. A number of hypotheses may explain these differences including dietary factors, micronutrient use, and genetic differences - especially those that modify the response of the androgen receptor. This program, the San Antonio Center of Biomarkers of Risk for prostate cancer (SABOR) will leverage the collaboration of five institutions with access to large numbers of ethnic minorities to conduct serial examinations for prostate cancer, examine biomarkers of risk and outcome, and to link these data with an extensive, robust clinical database. Specific biomarkers to be examined include IGF-1, IGFBP-3 and -4, androgen receptor trinucleotide repeat length, as well as nutritional analyses and selenium exposure. This ethnically-diverse population, the biorepository, and clinical database system will focus upon those unique factors of prostate cancer risk and will bring these unique and valuable resources to the network of investigators in the Early Detection Research Network.